A novel simple assay system for the detection of human platelet antigen 15 (HPA-15) alloantibodies based on three techniques: an HPA-15 expressing cell line, a monoclonal antibody-specific antigen-capture method and mixed-passive haemagglutination.

BACKGROUND AND OBJECTIVES: To detect HPA-15 alloantibodies, we previously developed a human platelet antigen 15 (HPA-15)-expressing cell line-based modified rapid monoclonal antibody immobilization of platelet antigen (CL-MR-MAIPA) assay. In this study, the protocol was modified for easier performance by introducing the mixed-passive haemagglutination (MPHA) principle. MATERIAL AND METHODS: In total, 20 samples that tested negative for HPA alloantibodies and eight that tested positive for HPA-15 alloantibodies (two and six positive for HPA-15a and HPA-15b antibodies, respectively) by CL-MR-MAIPA assay were used in this study. HPA-15 cell lines were incubated with serum/plasma and then solubilized. The lysate was transferred to a round-bottom well, which was coated with anti-human CD109 monoclonal antibodies. After incubation and repeated washings, sheep red blood cells, coated with anti-human IgG, were added to the wells. Haemagglutination was assessed the next day. RESULTS: The proposed cell line-based immune complex capture-dependent mixed-passive haemagglutination (CL-IC-MPHA) assay consisted of four steps, but required only 2 h to perform, except for overnight incubation for haemagglutination. Two HPA-15a alloantibody samples were reactive only for HPA-15a cells, and six HPA-15b alloantibody samples were reactive only for HPA-15b cells with the CL-IC-MPHA assay. The 20 samples that tested negative for HPA alloantibodies did not react with HPA-15a or HPA-15b cells. These data indicated that the CL-IC-MPHA assay was highly specific and sensitive. Unfortunately, the CL-IC-MPHA assay's analytic sensitivity was twofold to eightfold lower than that of the CL-MR-MAIPA assay. CONCLUSION: A novel, easy-to-perform protocol was successfully developed to detect HPA-15 alloantibodies with high specificity and sensitivity.

Cell-Based Versus Enzyme-Linked Immunosorbent Assay for the Detection of Acetylcholine Receptor Antibodies in Chinese Juvenile Myasthenia Gravis.

BACKGROUND: Patients in China with juvenile-onset myasthenia gravis present early, with a high prevalence of purely ocular symptoms, spontaneous remission rates, and low antibody seropositivity. Antibody detection using a cell-based assay has been reported to increase the diagnostic sensitivity in adult-onset myasthenia gravis. However, this method in patients with juvenile-onset myasthenia gravis has not been investigated. METHODS: Patients with juvenile-onset myasthenia gravis who had not received prednisone or immunosuppressive therapy were recruited between June 2015 and April 2018 at the Huashan Hospital. Clinical information was collected. Serum anti-acetylcholine receptor antibodies were detected via cell-based assay with HEK293T cells expressing acetylcholine receptor subunits and rapsyn. Additionally, the IgG antibody subclass was identified. RESULTS: Eighty-two patients with juvenile-onset myasthenia gravis were enrolled in the current study. Among them, 48 patients were anti-acetylcholine receptor positive (58.5%) and 34 were seronegative (41.5%), as assessed via enzyme-linked immunosorbent assay. Cell-based assay yielded 63 positive subjects (76.8%) and 19 seronegative subjects (23.2%). All the enzyme-linked immunosorbent assay-positive samples showed robust immunofluorescence in the cell-based assay, whereas 15 of 34 enzyme-linked immunosorbent assay-negative patients (44.1%) were found to have low-affinity acetylcholine receptor antibodies. Among all the cell-based assay-positive patients, 41 were positive for both adult and fetal acetylcholine receptor antibodies (50.0%), 18 were found positive for only adult acetylcholine receptor antibodies (21.9%), and four were found to possess only fetal acetylcholine receptor antibodies (4.9%). Fifteen antibody-positive samples underwent subclassification and were confirmed to be IgG1 subclass predominant (n = 15, including eight adult and fetal acetylcholine receptor antibody positive, five only adult acetylcholine receptor antibody positive, and two only fetal acetylcholine receptor antibody positive). There were no significant differences in clinical features among patients with different antibody profiles. CONCLUSIONS: The cell-based assay showed increased sensitivity in acetylcholine receptor antibody detection in Chinese patients with juvenile-onset myasthenia gravis, and most cases of Chinese juvenile-onset myasthenia gravis are still acetylcholine receptor autoantibody mediated. Furthermore, the antibodies detected are predominately of the IgG1 subclass.

Immunoadsorption or plasma exchange in steroid-refractory multiple sclerosis and neuromyelitis optica.

BACKGROUND: Plasma exchange (PE) and immunoadsorption (IA) are alternative treatments of steroid-refractory relapses of multiple sclerosis (MS) or neuromyelitis optica (NMO). METHODS: Adverse events and neurological follow-ups in 127 MS- (62 PE, 65 IA) and 13 NMO- (11 PE, 2 IA) patients were retrospectively analyzed. Response was defined by improvements in either expanded disability status scale (EDSS) by at least 1.0 or visual acuity (VA) to 0.5, confirmed after 3 and/or 6 months. RESULTS: Hundred and forty patients were included in safety analysis, 102 patients provided sufficient neurological follow-up-data. There were no significant differences between IA and PE in side effects (3.9% vs 3.6%, P = .96) or response-rate (P = .65). Responders showed significant lower age (P = .02) and earlier apheresis-initiation (P = .01). Subgroup-analysis confirmed significant lower age in patients with relapsing-remitting MS (RRMS) /clinical isolated syndrome (CIS). CONCLUSION: IA and PE seem equally safe and effective in steroid-resistant MS- or NMO-relapses. Early apheresis and low patient age are additional prognostic factors.

Understanding solid-phase HLA antibody assays and the value of MFI.

As the practice of medicine becomes more reliant on imaging and laboratory tests, medical decisions will be increasingly based on numbers. Accordingly, following the introduction of solid-phase testing to the HLA testing repertoire, laboratory directors and physicians have employed preset mean fluorescence intensity (MFI) thresholds as the basis for decisions in the management of transplant patients. However, what do MFI values mean? The literature is rife with reports detailing numerous factors that influence antibody assessment including (but not limited to) sensitization history of the patient, level of mismatch between donor and recipient, presence of interfering substances in the serum, whether the antigen on multiplex beads is native or denatured, day-to-day and technologist variability, and the historical performance of an assay in a given institution. How are these variables incorporated into the interpretation of MFI values? Herein, the pitfalls and complexities of single antigen bead (SAB) testing and interpretation are discussed with specific attention to what can and cannot be inferred by MFI.

Urea Artifacts Interfere with Immuno-Purification of Lysine Acetylation.

Comprehensive analysis of post-translational modifications (PTMs) often depends on the purification of modified peptides prior to LC-MS/MS. The implementation of these enrichment methods requires thorough knowledge of the experimental conditions to achieve optimal selectivity and sensitivity. In this regard, large-scale analysis of lysine acetylation, a key PTM for multiple cellular processes, makes use of monoclonal pan-antibodies designed against this moiety. We report that the immuno-purification of lysine-acetylated peptides is hampered by the copurification of lysine carbamylated peptides, a frequent urea artifact. This specific interaction can be explained by the similar chemical structures of lysine acetylation and lysine carbamylation. As an alternative, we propose a sample preparation protocol based on sodium deoxycholate that eliminates these artifacts and dramatically improves the selectivity and sensitivity of this immuno-purification assay.

Immunoadsorption therapy for dilated cardiomyopathy using tryptophan column-A prospective, multicenter, randomized, within-patient and parallel-group comparative study to evaluate efficacy and safety.

Over the past few decades, several cardiac autoantibodies have been reported in sera from patients with dilated cardiomyopathy (DCM). Immunoadsorption (IA) therapy is one of the therapeutic tools to remove such autoantibodies. The objective of this study was to investigate functional effects of IA therapy using a tryptophan column in severe DCM patients. Of 49 patients enrolled, 44 were randomized from 10 sites in Japan. IA therapy was conducted in 40 patients with DCM (refractory to standard therapy for heart failure, New York Heart Association [NYHA] class III/IV, left ventricular ejection fraction [LVEF] <30%). Mean echocardiographic LVEF was significantly improved (23.8 ± 1.3% to 25.9 ± 1.3%, P = 0.0015). However, mean radionuclide LVEF over 3 months of IA therapy was not significantly improved (20.8 ± 1.1% to 21.9 ± 1%, P = 0.0605). The cardiothoracic ratio was also significantly decreased (P = 0.0010). NYHA functional class (P < 0.0001), subjective symptoms assessed by a quality of life questionnaire (P = 0.0022), maximum oxygen consumption (P = 0.0074), and 6-minute walk distance (P = 0.0050) were improved after IA therapy. Subgroup analysis revealed improvement of echocardiographic LVEF in patients with higher baseline autoantibody scores but not in those with lower scores. IA therapy improved subjective symptoms and exercise capacity in patients with refractory heart failure resulting from DCM. Favorable effect on cardiac function was noted in patients with higher autoantibody scores. J. Clin. Apheresis 31:535-544, 2016. © 2015 Wiley Periodicals, Inc.

Comparison of double filtration plasmapheresis with immunoadsorption therapy in patients with anti-glomerular basement membrane nephritis.

BACKGROUND: Double filtration plasmapheresis (DFPP) and (IA) are both used to clear antibody. However, the clinical efficacy and safety of DFPP in patients with anti-glomerular basement membrane (anti-GBM) disease are unclear. METHODS: The 28 enrolled patients diagnosed serologically and pathologically with anti-GBM disease from 2003 to 2013 included 16 treated with DFPP and 12 with IA, with all patients administered immunosuppressive agents. DFPP consisted of an EC50W filter for plasma separation and an EC20W filter for plasma fractionation. A double volume of plasma was processed, and each patient received a 30-40 g human albumin supplement during each session. IA consisted of 10 cycles per session, with 8-10 sessions performed daily or every other day and each session regenerating 30-60 L of plasma. Serum anti-GBM antibodies and IgG were measured, and urinary and blood tests were performed, before and after each procedure. Renal function and outcome were determined. RESULTS: The 28 patients consisted of 13 males and 15 females, of median age 44.5 years (range, 22.5-57 years). Six patients had pulmonary hemorrhage and 18 had serum creatinine concentrations >500 umol/L. The average serum creatinine concentration at early onset of disease was 525 umol/L while the peak concentration was 813 umol/L. All patients showed progressive increases in serum creatinine and required CRRT during the course of disease. Pathological examination showed an average 73.9% of crescents (range, 54.6-95.4%).The clinical and pathological features of the DPPP and IA groups were similar. Efficacy of clearing anti-GBM antibody was similar in the two groups (59.0 vs. 71.2%, P = 1.00), although fewer patients in the DFPP group experienced reduced IgG (62.7 vs. 83.5%, p = 0.002). One patient each had a pulmonary hemorrhage and a subcutaneous hemorrhage during treatment, but there were no other serious complications. At the end of follow-up, patient survival and renal survival were similar in the DFPP and IA groups. CONCLUSION: DPPP plus immunosuppressive therapy efficiently and safely removed anti-GBM antibodies. The fewer plasma-associated side effects and reduced loss of IgG suggest that DFPP may be a better treatment choice for anti-GBM disease, especially in patients with insufficient plasma.

Multiplexing analysis of the polyspecific intrathecal immune response in multiple sclerosis.

Intrathecal synthesis of the antibodies specific to neurotrofic viruses: measles (M), rubella (R), Varicella-Zoster (Z), and/or H. simplex (H), known as "MRZH-reaction" plays important diagnostic role in multiple sclerosis (MS). Whereas the analysis of the oligoclonal IgG bands provides high sensitivity, the MRZH-reaction shows high specificity, and hence these methods complement each other. For the first time we applied multiplexing bead-based technology to simultaneously analyze cerebrospinal fluid (CSF) and serum concentrations of antibodies against these viruses, and to calculate the antibody specific indices (ASI's). The method shows reasonable precision: intra-assay, 2.9-6.7%, and inter-assay, 2.0-3.2%. The results are comparable with these obtained with other methods (ELISAs), including two runs of the certified external quality control schemes. Eighty-one percent of the MS cases (n=27) and none of the sex- and age-matched controls (n=14), except one subject with "borderline" anti-measles ASI of 1.5, showed intrathecal synthesis of IgG against at least one of the viruses discussed. The ratios of the MRZH-positive cases in the MS group were: 12/22 for M, 12/19 for R, 13/26 for Z, and 7/26 for H. We conclude that the multiplexing technology can be applied as a tool to study the intrathecal immune response in the diagnosis of MS.

Synthesis of hepcidin derivatives in order to develop standards for immune adsorption method.

MeCN, acetonitrile; ECL, enhanced chemiluminescence; EDT, 1,2-ethanedithiole; HEPC12-A, rabbit anti-human hepcidin IgG, affinity purified; HEPC13-A, rabbit anti-mouse/human hepcidin IgG, affinity purified; HEPC61-P, human hepcidin-25 control/blocking synthetic peptide; HRP, horseradish peroxidase; IL-6, interleukin-6; KLH, keyhole limpet hemocyanin; LEAP, liver-expressed antimicrobial peptide; NEM, N-ethylmaleimide; NMP, N-methyl-pirrolidone; PBS, phosphate buffered saline; PVDF, polyvinylidene difluoride; SELDI-TOF-MS, surface-enhanced laser desorption ionization-time-of-flight mass spectrometry; TMB, tetramethylbenzidin; TNF-alpha, tumor necrosis factor-alpha.

Multicenter study of a new fully automated HBsAg screening assay with enhanced sensitivity for the detection of HBV mutants.

In a multicenter study a new, fully automated Roche Diagnostics Elecsys HBsAg II screening assay with improved sensitivity to HBsAg mutant detection was compared to well-established HBsAg tests: AxSYM HBsAg V2 (Abbott), Architect HBsAg (Abbott), Advia Centaur HBsAg (Bayer) Enzygnost HBsAg 5.0 (Dade-Behring), and Vitros Eci HBsAg (Ortho). A total of 16 seroconversion panels, samples of 60 HBsAg native mutants, and 31 HBsAg recombinant mutants, dilution series of NIBSC and PEI standards, 156 HBV positive samples comprising genotypes A to G, 686 preselected HBsAg positive samples from different stages of infection, 3,593 samples from daily routine, and 6,360 unselected blood donations were tested to evaluate the analytical and clinical sensitivity, the detection of mutants, and the specificity of the new assay. Elecsys HBsAg II showed a statistically significant better sensitivity in seroconversion panels to the compared tests. Fifty-seven out of 60 native mutants and all recombinant mutants were found positive. Among 156 HBV samples with different genotypes and 696 preselected HBsAg positive samples Elecsys HBsAg II achieved a sensitivity of 100%. The lower detection limit for NIBSC standard was calculated to be 0.025 IU/ml and for the PEI standards ad and ay it was <0.001 and <0.005 U/ml, respectively. Within 2,724 daily routine specimens and 6.360 unselected blood donations Elecsys HBsAg II showed a specificity of 99.97 and 99.88%, respectively. In conclusion the new Elecsys HBsAg II shows a high sensitivity for the detection of all stages of HBV infection and HBsAg mutants paired together with a high specificity in blood donors, daily routine samples, and potentially interfering sera.

Prospective evaluation of the immunobead assay for the diagnosis of adult chronic immune thrombocytopenic purpura (ITP).

Chronic immune thrombocytopenic purpura (ITP) is an autoimmune disease characterized by antibody-induced platelet destruction. To better define the role of antigen-specific assays in adult chronic ITP, we prospectively measured platelet-associated autoantibody against either glycoprotein (GP) IIb/IIIa or GPIb/IX in 282 patients with chronic ITP and 289 patients with thrombocytopenia of other causes. We divided chronic ITP into four subgroups: presplenectomy, mild (platelet count >30 000 micro (L-1) requiring no therapy), presplenectomy, severe (platelet count <30 000 micro L(-1) requiring therapy but not splenectomy), postsplenectomy, remission (postsplenectomy partial or complete remission without further therapy) and postsplenectomy refractory (required therapy after splenectomy failure). Positive results: total ITP group, 55.4%; presplenectomy, mild, 31.1%; presplenectomy, severe, 42.6%; postsplenectomy, remission, 50.0%; and postsplenectomy, refractory, 87.8%. In addition, the degree of positivity increased with the severity of the patient's disease. The assay had a minimum specificity of 84.4% if clinical factors, consistent with immune thrombocytopenia, were not considered in patients with thrombocytopenia associated with other diseases. However, if clinical factors consistent with immune thrombocytopenia were considered and only patients with questionable immune thrombocytopenia and patients 'lost to follow-up' were included in the false-positive group the specificity was 93.1%. We conclude that the presence of immune thrombocytopenia is highly probable if the immunobead assay is positive and that antigen-specific assays are diagnostically useful in adult chronic ITP.

Adsorption of autoantibodies in the presence of LISS to detect alloantibodies underlying warm autoantibodies.

BACKGROUND: The safe transfusion of patients with warm autoimmune hemolytic anemia requires an efficient and time-saving assay to detect alloantibodies underlying autoantibodies. Methods used include RBCs treated with ZZAP reagent, proteolytic enzyme, or untreated RBCs in the presence of PEG. We propose a method using LISS, which presents some advantages over previous methods. STUDY DESIGN AND METHODS: We evaluated the effectiveness of autoantibody adsorption with papain-treated and untreated RBCs in the presence of LISS for removal of autoantibodies, without affecting alloantibodies. RESULTS: One-hundred twenty sera containing autoantibodies were adsorbed with our routine method, which uses papain-treated allogeneic RBCs. Seven-hundred twenty adsorptions (mean, 6 per sample) and 21,600 minutes (mean, 180 min per sample) were required to remove autoantibodies. Fifty sera were adsorbed with our routine method that uses papain-treated allogeneic RBCs in the presence of LISS. The number of adsorptions and the completion time were, respectively, 144 (mean, 2.9 per sample) and 2,880 minutes (mean, 57.6 min per sample). Twenty sera were evaluated with untreated autologous RBCs, in the presence of LISS; 58 adsorptions (mean, 2.9) and 1,160 minutes (mean, 58 min per sample) were required. Three adsorptions with antigen-negative allogeneic RBCs were performed on 8 sera containing alloantibodies with weak reactivity (anti-K [1], anti-D [1], anti-Fya[2], anti-S [2], anti-E [1], and anti-Jka[1]). Alloantibodies were detected with the LISS procedure with papain-treated and untreated RBCs and the routine papain method. Alloantibodies with weak reactivity, tested against the same antibody-detection RBCs, remained unchanged following adsorption of 5 sera. An anti-S, with very weak reactivity, was no longer detected, and an anti-Jka became weaker (1+), regardless of the procedure used. One anti-D became weaker only with the LISS adsorption method. CONCLUSION: Autoantibodies can be adsorbed more efficiently in the presence of LISS.

Development of an in vitro miniature model to simulate immunoadsorption in patients with systemic lupus erythematosus.

In SLE, immunoadsorption is used as an adjuvant therapy; however, adsorption profiles and binding mechanisms have not yet been completely investigated. Using a minicolumn filled with the sorbent IMPH with or without the ligand phenylalanine, we developed a model simulating clinical conditions in a reduced scale with a constant ratio of plasma to column volume and a constant plasma flow at room temperature. By desorbing the column, the adsorption efficacy for different antibodies could be measured directly. We demonstrate that the adsorption rate can be increased by a low plasma flow and by covering the column surface. Double perfusion of the same column did not increase the amount of adsorbed antibodies. We further demonstrate that the carrier material without a ligand is unable to bind antibodies or protein. In the IMPH sorbent anti-dsDNA antibodies were significantly better adsorbed than total IgG or total protein. After a single perfusion of 21 samples, we estimated a mean anti-dsDNA antibody adsorption rate of 22.5% (+/-13.6). A group of ten responders with a medium adsorption rate of 35.4% (+/-6.5) clearly differed from a second group of eleven nonresponders (10.9% +/- 4.2). Anti-cardiolipin antibodies (ACA) were adsorbed in a wide range (IgG type, 2.5-52.7%, IgM type, 1.1-37.8%) while anti-Ro (SSA) antibody adsorption was negligible. This in vitro minimodel provides a precise simulation of therapeutic immunoadsorption and helps to analyze the binding characteristics of the sorbent IMPH and shows its effectiveness in several antibody subsets of different patients.

Enhanced affinity capture MALDI-TOF MS: orientation of an immunoglobulin G using recombinant protein G.

Although immobilization of antigen-specific immunoglobulins onto matrix-assisted laser desorption/ionization (MALDI) targets allows the specific detection and enrichment of an antigen from complex biological fluids, the process of antibody immobilization is not optimal. The principal reason is that the antibody can bind to the template in various orientations, many of which block antigen recognition. An affinity capture MALDI mass spectrometry methodology was developed by covalently immobilizing an Fc receptor (recombinant protein G) onto MALDI gold targets for the purpose of orientating an immunoglobulin G, with the Fab domains pointing away from the target surface. The pregnancy and cancer marker, human chorionic gonadotropin beta core fragment (hCGbetacf), was our chosen test substance. To optimize the methodology, different surface densities of protein G and immunoglobulin were achieved by employing varying concentrations for immobilization. Captured amounts of hCGbetacf were compared using an external standard (cytochrome c). Orientation of immunoglobulin resulted in an approximately 3-fold increase in MALDI signal compared to using randomly immobilized antibody. Higher antibody concentrations resulted in diminished MALDI signals, which were explained by steric hindrance. Purification and enrichment of hCGbetacf was achieved from a test solution containing contaminant peptides and proteins using oriented immunoglobulins on-target.

Positive selection of CD34+ cells by immunoadsorption: factors affecting the final yield and hematopoietic recovery in patients with hematological malignancies and solid tumors.

There is a progressive increase in the use of selected hematopoietic progenitor cells after myeloablative therapy in patients affected by malignancies. Our goal was to determine which blood parameters, in the starting cell population, influence the concentration of CD34+ progenitors and the removal of unwanted cells in the final product. Also, we evaluated the hematopoietic recovery and toxicity associated with peripheral blood stem cell infusion. We retrospectively reviewed 53 procedures of positive selection of CD34+ cells, performed with the Ceprate SC immunoadsorption system, in 47 paticnts affected by various hematologic malignancies and solid tumors. An increased percentage of CD34+ cells in the starting fraction was associated both with the final purity and enrichment of CD34+ cells and with a decreased percentage of CD3+ and CD19+ cells in the final product. A low platelet count before selection had a borderlinc influence on the recovery of CD34+ cells. Forty patients received a median of 5 x 10(6) CD34+ cells per kg; the absolute neutrophil count (ANC) reached 0.5 x 10(9)/l in a median of 10 days whereas a PLT count above 20 x 10(9)/l was observed in 14 days. The reinfusion of selected CD34+ cells, containing a very low amount of dymethylsulfoxide. was well tolerated and no adverse reactions were observed. Autologous transplantation with selected CD34+ cells is a safe and well-tolerated procedure in patients affected by hematologic malignancies and solid tumors. Positive selection of CD34+ cells seems to be related to the quality of the apheresis products, particularly to the initial CD34+ cell and PLT content.

Plasmapheresis and immunoadsorption: different techniques and their current role in medical therapy.

In the last 30 years, several studies have documented the effect of plasmapheresis and immunoadsorption in eliminating pathogenic autoantibodies (ABs) and immune complexes (ICs) from circulation. These extracorporeal therapies are still not accepted as first line options, which may be due to existing controlled studies failing to confirm any obvious benefit. Today, indications for plasmapheresis are idiopathic-thrombocytopenic purpura (ITP), thrombotic-thrombocytopenic purpura (TTP), and also cryoglobulinemia during the course of systemic rheumatic diseases and Goodpasture's syndrome. In acute flares and severe organ manifestations, extracorporeal therapies may be helpful as a complement to immunosuppressive therapy. Immunoadsorption offers some advantages compared with plasmapheresis; however, to date only avoidance of substitution fluids has really been used. The new therapeutic options given by immunoadsorbers, that is, a continuous application in acute disease states or chronic use instead of immunosuppressive drugs, have still to be evaluated in systemic autoimmune diseases. Most experiences have used immunoadsorbent columns in the pretransplantation treatment of patients with high panel reactivity and in patients with ITP. Results indicate excellent biocompatibility and a good clinical response. Randomized controlled trials are mandatory to give continued support to the therapeutic opportunities offered only by immunoadsorption; the limited number of patients suitable for this therapy necessitates multicentric cooperation.

EAST and CAP specificity for the evaluation of IgE and IgG antibodies to diisocyanate-HSA conjugates.

Sera of 54 symptomatic workers showing sensitization to isocyanate-human serum albumin (HSA) conjugates were subjected to parallel enzyme allergosorbent test (EAST) and CAP measurements to determine IgE antibodies to diphenyl-methane diisocyanate-HSA, toluene diisocyanate-HSA and hexamethylene diisocyanate-HSA. Results of both methods correlated rather well with each other. In comparison to the EAST results, the CAP values were twice as high, and 4, 17 and 13% more frequently positive findings were obtained with the three different antigens. Autoinhibition performed with both methods proved the specificity of IgE binding in 92% of sera in EAST and in 89% of sera in CAP if values of > or = 0.35 kU/l were considered. The total IgE level in sera influenced the antibody results. Four of 20 sera studied by autoinhibition had a total IgE of > 700 kU/l, and two of them did not show significant autoinhibition with all conjugates by CAP and one serum by EAST. In addition, three of these sera showed an elevated binding to control HSA only (0.31-0.5 kU/l), and two revealed only a slightly increased IgE binding when compared with the HSA control (ratio of isocyanate-HSA to HSA, < 2). Only 2 of the 16 sera with a total IgE level of < 700 kU/l yielded a noninhibitory positive CAP result, whereas all positive EAST values of these sera could be significantly blocked by autoinhibition. Therefore, we suggest regarding EAST and CAP IgE results to isocyanate-HSA as positive if they exceed HSA control by 100% and are above 0.35 kU/l. Weak positive CAP results (< or = kU/l), especially of sera with total IgE > 700 kU/l, should by confirmed by inhibition experiments. Twelve of 40 symptomatic isocyanate workers exhibited borderline or weakly increased IgG values for diisocyanate-HSA conjugates in the CAP system and IgG-EAST. HSA tested in EAST as a reference showed nearly the same results as the isocyanate-HSA conjugates. In the 23 inhibition experiments, IgG-binding specificity was not confirmed. These findings imply IgG measurement to be of no diagnostic value in isocyanate-induced airway disorders.

Effect of dilution, temperature, and preservatives on the long-term stability of standardized inhalant allergen extracts.

BACKGROUND: Although documented stability of allergens used for diagnosis is important, research in this area has been limited. Most studies on extract stability have been of limited duration and discrepancies have been reported between stability test results of in vivo and in vitro methods. OBJECTIVE: In this study we determined the stability of allergenic extracts, comparing the intracutaneous test and enzymallergosorbent test inhibition method and determining the effect of temperature, dilution, and preservatives. METHODS: Three formulations of timothy pollen, birch pollen, house dust mite (D. pteronyssinus) and cat dander extracts, as used for bronchoprovocation, skin prick testing and intracutaneous testing, were stored for 24 months at 6 degrees C. The influence of temperature on various formulations was determined using the enzymallergosorbent test inhibition technique during storage for up to 36 months. RESULTS: Most formulations were found to be stable for 24 (intracutaneous test) or 36 (enzymallergosorbent test inhibition) months at 6 degrees C. At 25 degrees C, most formulations showed a decrease in relative potency, which remained above the limit of 0.3 times the in-house-reference for the bronchoprovocation formulation of timothy pollen, birch pollen, and house dust mite and for the skin prick test formulation of cat dander. CONCLUSIONS: Cat dander was remarkably stable at 6 and 25 degrees C in glycerine and birch pollen was very susceptible to phenol. This destructive effect of phenol could be prevented by adding human serum albumin. The discrepancy between in vivo and in vitro tests reported by others was confirmed for house dust mite and timothy pollen.